Two systems for the uptake of phosphate in Escherichia coli

Abstract

Mutants of Escherichia coli K-12 were constructed such that each possessed one single major system for phosphate transport. A comparison of these strains showed that one of the systems (PIT) was fully constitutive, required no binding protein, and operated in spheroplasts. It permitted the complete exchange of intracellular phosphate with extracellular phosphate (or arsenate) and was completely inhibited by uncouplers. The other system, PST, was repressible by phosphate concentrations above 1 mM, required the phosphate-binding protein for full activity, and did not operate in spheroplasts. It catalyzed very little exchange between internal and external phosphate and was resistant to uncouplers. The maximal velocities attained by the two systems were approximately the same, but the affinity for phosphate in the PST system was greater by two orders of magnitude. In strains in which both systems were fully operative, the initial rates of uptake were nearly additive, and the systems appeared to interact with a common intracellular phosphate pool.

Bioenergetic models for acetate and phosphate transport in bacteria important in enhanced biological phosphorus removal

“…was linear over the initial 30 min ( Fig. S10) and is comparable to that observed for E. coli (Rosenberg et al, 1977). The PHA produced during the anaerobic incubation was depleted after 120 min of aeration as determined by post-FISH staining with Nile blue A (Fig.…”

Evidence for the transport of zinc(II) ions via the Pit inorganic phosphate transport system in Escherichia coli

“…This indicates that the Pit system represents a second, low-a¤nity uptake system for zinc(II) in E. coli, in contrast to the ZnuABC high-a¤nity uptake system that has been described recently [10]. The Pit system is expressed constitutively in E. coli [29], whereas expression of ZnuABC is repressed at high concentrations of Zn(II) [10].…”

Metabolic potential and in situ activity of marine Marinimicrobia bacteria in an anoxic water column

“…Arsenate concentrations in coastal and open oceans are typically low to nondetectable in surface waters, but increase with depth, often in an inverse relationship with dissolved oxygen (Andreae, 1979). Phosphate uptake systems often cannot distinguish arsenate from phosphate (Rosenberg et al, 1977). On entry into the cell, arsenate can disrupt cellular processes by replacing phosphate in biochemical reactions such as oxidative phosphorylation, and the reduction product, arsenite, can induce toxicity by binding a wide array of proteins (Oremland and Stolz, 2003).…”